Intraorbital spherule

ABSTRACT

An intra-ocular ball for constituting a prosthesis after enucleation or evisceration of an eye is made of porous sintered alumina having interconnected pores with a diameter of about 300 microns, and capable of receiving a driver after colonization.

The present invention relates to a ball that is to constitute an implantor prosthesis for replacing the eyeball after enucleation orevisceration.

BACKGROUND OF THE INVENTION

During an enucleation operation the entire eyeball is extracted from theorbital cavity. In evisceration, only the contents of the eyeball isextracted, the scleral shell remaining in place.

In both cases, in order to avoid leaving an empty orbital cavity, it hasbeen known for along time to insert a synthetic prosthesis of sphericalshape corresponding to the shape of the normal eye, either directly intothe orbital cavity after enucleation or into the scleral shell afterevisceration.

On the front of this synthetic prosthesis there is placed that which iscommonly called a "glass eye", which in fact, is constituted by aplastic half-shell on which an iris and a pupil are marked, with theshell serving an esthetic purpose only.

The problem posed by such prior prostheses stems from being made of amaterial that is biocompatible but not colonizable, such as plastic(PMMA) or silicone, thus not enabling the prosthesis to be connected tothe half-shell.

It is also known to make an intra-orbital implant comprising a siliconecore covered in a biocolonizable material such as expanded PTFE. Thedrawback of such a prosthesis is that colonization can take place onlyat the periphery where the biocolonizable material is to be found thuslikewise making it impossible to establish a connection between such animplant and the plastic shell.

In patent U.S. Pat. No. 4 976 731 (Perry), it is proposed to make theball out of sterile porous hydroxyapatite ceramic obtained either fromcoral or by synthesis. The porosity of the hydroxyapatite prosthesisenables the implant to be colonized in its entirety. That colonizationmakes it possible subsequently to drill a hole into the ball enabling adriver to be inserted connecting the ball to the plastic half-shell. Thedriver provides better transmission of movements from the ball to theplastic shell, thereby enabling the artificial eye to move in a mannerequivalent to the other eye.

Nevertheless, fabricating such an implant presents great difficulty ofimplementation associated with very high production costs.

That is in addition to the solubility of hydroxyapatite in the organism,which solubility is of the order of 3%, and gives rise to inflammatoryreactions.

OBJECT AND SUMMARY OF THE INVENTION

An object of the present invention is to mitigate those drawbacks and toenable the cost of such implants to be reduced and to propose a materialthat is highly innocuous, and much more stable over time.

According to the invention, the intra-orbital ball suitable forreplacing the eye in the event of enucleation or evisceration is made ofa porous sintered metal ceramic.

BRIEF DESCRIPTION OF THE DRAWING

Other characteristics and advantages of the invention appear from thefollowing description given purely by way of non-limiting example andwith reference to the sole FIGURE which is a diagram of an implant ofthe invention.

MORE DETAILED DESCRIPTION

In the figure, there can be seen the colonizable porous ball 2 on whicha half-shell 1 is fixed by means of a driver 3 constituted by a rodhaving one end fixed inside the ball and having its other end pivoted tothe half-shell.

The ball is preferably made from sintered metal oxide powder havingpores that are fully interconnected and of substantially constantsection. Optimum colonization appears to be obtained with pores of about300μ, however colonization can occur with pores that are much smaller ormuch larger. Once the organism has colonized the ball, it can be drilledto receive the driver 3 in the same manner as a ball made ofhydroxyapatite.

The metal ceramic is preferably constituted by alumina in powder form,with a sintering additive incorporated therein and constituting about 1%by weight, e.g. magnesium oxide (MgO).

In addition, alumina is widely available on the market in the ultrapurestoichiometric state, it is absolutely inert both chemically andbiologically, and no solubility has been observed. In addition, sinteredalumina has very great mechanical strength.

The sintered alumina is prepared from a synthetic foam and an aluminapowder of determined grain size. The foam is impregnated with a slip andit is subjected to sintering. The heating melts the plastic and causesthe alumna to agglomerate, while leaving the channels or pores of thefoam in place. The diameter of the resulting pores is a function of thepores in the original foam.

A drawback that could be presented by a sintered alumina ceramic lies inits very great mechanical strength which makes it difficult to drill.Nevertheless, this problem can be resolved with porous alumina by usinga sintering additive such as magnesium oxide (MgO) at a concentration ofabout 1% by weight, since that makes it possible to reduce the sinteringtemperature by about 100° C. (1500° C. instead of 1600 ° C.), therebydegrading the mechanical properties of the alumina and making it easierto drill with a drill and a hexagonal milling cutter.

We claim:
 1. An intra-orbital ball comprising an implant shaped, sizedand configured to be implanted after enucleation or evisceration, saidball having at least a substrate made of a porous sintered metalceramic.
 2. A ball according to claim 1, wherein the ceramic is based onalumina powder.
 3. A ball according to claim 1, wherein the pores of theceramic are interconnected and not closed, having a diameter of about300 microns.
 4. A ball according to claim 2, wherein a sinteringadditive is mixed with the alumina powder at a concentration of 1% byweight.
 5. A method of fabricating a ball according to claim 1,comprising in soaking a foam sphere in an alumina slip and thensubjecting said sphere and slip to heating that eliminates the foam.